质子型固体电解质膜反应器电催化氧化H2S过程中对称电极失活机理与再生研究

Enlighted by the fact that the accommodation of sulfide species distribution on the anode to form renewable sulfides, the project focuses on deactivation mechanism and regeneration of symmetric electodes with perovskite structure, aiming to solve the key issue about the easily deactivated anode in solid eletrolyte membrane reactor (SEMR) degrading H2S. Based on the semi-conductor catalysis and crystal defect theory, the project plans to fabricate proton-conducting SEMR, which is coated by symmetric electrodes with perovskite structure, La1-xSrxMO3(M= Mn、Ti、V, etc) to electro-catalytically oxidize H2S. H2S adsorption on the oxygen vacancies of the symmetric electrodes will be investigated by sequential switch of reactants compositions in transient response method and by characterizations including in-situ Raman, XPS, etc. Density funtional theory will be applied to set up the model of active sites modification in adsorption. By the aid of in-situ electrochemical measurement, the causes to deactivation of symmetrical electrodes oxidizing H2S in an electro-catalytical way can be revealed and the kinetic models can also be proposed, in combination with steady proton transport in SEMR. Furthermore, after interconverting the fuel and oxidative gas, the desorption of renewable sulfur on the surface of electrodes will be studied in the meanwhile. The feasibility of regenaration will be illuminated when the separate (only O2) and synergetic (O2-steam) desorption processes are respectively adopted. The project will manage to propose a theoretical support on deactivation mechnism of anode and on how to design symmetric electrodes tolerant to H2S, which promotes electro-catalytical oxidation of H2S more efficiently in SEMR with lower energy consumption.

本项目针对固体电解质膜反应器(SEMR)处理H2S时阳极易失活这一瓶颈问题，以调节阳极硫形态分布，获取易脱附的产物硫为思路，开展钙钛矿对称电极的失活机理与再生途径研究。根据半导体催化和晶体结构缺陷理论，制备Mn、Ti、V等过渡金属掺杂的La1-xSrxMO3钙钛矿对称电极，构建对称电极负载的质子型SEMR电催化氧化H2S。通过瞬态响应技术序贯切换反应物组成，结合原位Raman、XPS表征结果，揭示H2S在钙钛矿对称电极表面氧空位上的吸附机制，用表面泛函理论预测电极种类和成分对吸附活性位的调变规律；同时根据原位电化学测定，探寻稳态质子传导条件下电极失活原因，建立H2S电催化氧化动力学模型。通过互换阴阳极气体，探明O2和阴极产物水蒸汽对电极表面产物硫的脱附机制，探讨钙钛矿对称电极再生可行性。这将为H2S电催化氧化过程中阳极失活和耐硫电极设计提供理论依据，促进高效低耗处理H2S尾气的研发。

本研究根据半导体催化和晶体结构缺陷理论，分别Y、Ce、Sm掺杂A位，以 Mn、Co、Fe 等过渡金属掺杂B位，以及A，B位同时掺杂等手段，制备 La1-xSrxMO3 单钙钛矿系列和Sr2XMoO6（X=Co、Ni、Fe） 双钙钛矿系列耐硫阳极，并将其作为含硫气体燃料气对称电极，通过瞬态响应脉冲、原位 Raman、XPS、XRD、SEM、电化学阻抗等表征技术，系统地研究了这两大类电极材料在还原性H2S气氛下的相结构变化，催化活性、电催化活性以及与氧离子固体电解质膜、质子固体电解质膜的兼容性等。双钙钛矿电极中Sr2CoMoO6和单钙钛矿La0.75Sr0.25Cr0.5Mn0.5O3±δ具备作为对称电极的优点，氧空位对硫吸附是La0.75Sr0.25Cr0.5Mn0.5O3±δ阳极失活的重要原因，但中度Mn掺杂能使得单钙钛矿材料催化活性和耐硫性能保持平衡。通过离线再生技术，Sr2CoMoO6对称电极再生电性能达到79%。以上发现为耐硫钙钛矿对称电极的材料设计、制备工艺提供了充足的参考。与此同时，尝试制备了Zr 掺杂BaCe0.8-xY0.2O3-δ (BCZY)、Ba3Ca1.18Nb1.82O9-δ (BCN18)等负载钙钛矿对称电极的质子型固体电解质膜反应器，通过分析H2S电催化氧化产物吸/脱附、电催化氧化性能和膜反应器失活、再生机制，探明了质子固体电解质膜反应器的主要特点。结果发现：与氧离子固体电解质膜反应器相比较，质子固体电解质H+传输机理不仅能避免阳极在过氧化条件下的迅速失活，而且还原性气氛的营造为对H2S活性的金属硫化物电极的原位重塑提供了有利条件，保证了金属硫化物颗粒的原位生成。这一发现为H2S在固体电解质膜反应器阳极的设计提供了新的理念，为建立固体电解质膜反应器电催化氧化 H2S 尾气这一高效低耗处理手段提供理论依据。